It’s not only in America, but in many other countries too, that the trend of not having babies or of having the least number is being followed. The reason can be various, but the one which hits the mind suddenly after reading such question is the invasion of modernization in our lives.
This globalized and post-modern society which we inhabit has given a lot of positive freedom to women. Women now are not confined to the four walls of domesticity. They are coming out and contributing towards global economy, technology, humanity, and what not. This is a newly found independence for most of the women. Among all this, they want to be restricted as minimally as possible when it comes to domestic responsibilities.
Yes, this may sound heartless to many and insensitive to almost everyone. But the truth is that post-modern society, which does not believe in stereotypical gender roles, has taught both men and women to see women as more than a child generating and caring machine. For some, this may even be a shockingly negative turn of feminism, which is criticized often anyway.
Today, a working woman thinks about her career just like a man, whose half of the priority is family and half is his work and career. But biologically, women are obliged to produce children which they prefer to delay for the sake of themselves.
So women in America, and all over think about having children only after they have achieved something in life. We have come very far in terms of being open minded and modern, but we still hesitate to employ a mother and prefer a woman who does not have any child, or better, is not married. So if world can be selfish, women at least have some right to think about herself.